JP2011002042A - Chain tensioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a gap between a plunger and a sleeve from being extended by the effect of inner diameter contraction by press-fitting in spite of a structure such that the sleeve is easily fixed to a housing by press-fitting.SOLUTION: The chain tensioner includes the sleeve 12 having a bottomed cylindrical shape, which is mounted within the housing 11; and the plunger 13 sliding in a sleeve axial direction X within the sleeve 12, in which a biasing force in a chain laying direction X1 is given to the plunger 13 by hydraulic pressure within a hydraulic chamber 17. The sleeve 12 includes a sliding section 21 having a uniform inner diameter, on which the plunger 13 slides through a predetermined gap ΔS1, and press-in sections 22 and 23 which are fixed by being press fitted to press-fitted sections 28 and 29 of the housing 11. The press-in sections 22 and 23 are located out of the sliding section 21 with respect to the sleeve axial direction X.

Description

  The present invention relates to an improvement of a hydraulic chain tensioner.

  As shown in Patent Document 1, a chain that transmits the rotational force of a crankshaft of an internal combustion engine to a camshaft on a cylinder head is provided with a hydraulic chain tensioner that adjusts its tension by hydraulic pressure. The chain tensioner has a bottomed cylindrical sleeve mounted in a housing, and a plunger that slides in the sleeve, an inner bottom surface of the sleeve, and a back surface of the plunger that faces the bottom surface, The plunger is given a biasing force toward the chain side by the hydraulic oil sealed in the pressure chamber between the two. The sleeve is fixed, for example, by press-fitting it into the mounting recess of the housing over its entire length.

JP 2004-144190 A

  In such a hydraulic chain tensioner, this clearance is set so that the hydraulic oil in the hydraulic chamber does not leak excessively through the clearance between the outer periphery of the plunger sliding inside the sleeve and the inner periphery of the sleeve. It is necessary to manage with high accuracy. However, when the sleeve is press-fitted into the housing over the entire length, the inner diameter of the sleeve is reduced over the entire length of the sleeve during press-fitting. For this reason, it is necessary to ensure a large gap between the plunger and the sleeve in advance in such a manner that the inner diameter is reduced, and the gap must be increased in the assembled state after press-fitting. As a result, the hydraulic fluid in the pressure chamber is likely to leak through the gap, and the load on the plunger chain side is insufficient, or the hydraulic fluid in the hydraulic chamber is insufficient when the engine is started, and the back surface of the plunger and the inner bottom surface of the sleeve There is a risk of inconveniences such as stopping abnormal noise due to contact.

  On the other hand, in the case where the sleeve is cast and fixed to the housing, the inner diameter is reduced due to the pressure at the time of casting. When the sleeve is formed integrally with the housing, the entire housing needs to be formed of a metal material corresponding to the coefficient of thermal expansion with the plunger, which increases the cost and requires processing of the portion where the plunger slides.

  The present invention has been made in view of such circumstances, and a novel chain tensioner capable of suppressing the expansion of the gap between the plunger and the sleeve while having a structure in which the sleeve is simply fixed to the housing by press-fitting. It is intended to provide.

  That is, the chain tensioner of the present invention includes a housing, a bottomed cylindrical sleeve mounted in the housing, a plunger that slides in the sleeve in the axial direction of the sleeve, the inner bottom surface of the sleeve, and the bottom surface. A hydraulic pressure supply circuit for supplying hydraulic pressure to the hydraulic chamber between the opposing back surfaces of the plunger, and an urging force in the chain tension direction is applied to the plunger by the hydraulic pressure in the hydraulic chamber.

  The sleeve includes a sliding portion having a uniform inner diameter through which the plunger slides through a predetermined gap, and a press-fit portion that is fixed by press-fitting the press-fit portion of the housing. This press-fit portion is provided at a position deviated from the sliding portion in the sleeve axial direction.

  As described above, the sliding portion of the sleeve in which the plunger slides and the press-fit portion that is fixed to the housing by press-fitting are provided at different positions in the sleeve axial direction. Is not directly affected by the inner diameter reduction. Accordingly, the sleeve can be easily fixed to the housing by press-fitting, but the gap between the sleeve inner peripheral surface and the plunger outer peripheral surface is made sufficiently small by suppressing the influence of the inner diameter reduction due to the press-fitting. It is possible to suppress functional deterioration due to excessive leakage of hydraulic oil from the engine.

  The press-fitting portion is provided at a position deviating from the sliding portion in a direction opposite to the chain tension direction in the sleeve axial direction, and has an outer diameter smaller than that of the sliding portion. Thus, by making the press-fitting part thinner than the sliding part, the dimensional tolerance is reduced, the dimensional control becomes easy, the press load at the time of press-fitting is reduced, and the press-fitting work becomes easy.

  As described above, according to the present invention, although the sleeve is fixed to the housing by press-fitting, the expansion of the gap between the plunger and the sleeve is suppressed, so that leakage of hydraulic oil from the gap is suppressed, and the plunger is stable. The applied oil pressure is applied, and the chain tension can be properly maintained.

Sectional drawing which shows the chain tensioner which concerns on one Example of this invention. Sectional drawing which follows the II-II line | wire of FIG. Sectional drawing which follows the III-III line | wire of FIG. Sectional drawing which follows the IV-IV line of FIG. The front view which shows the chain for driving a cam, the sprocket, etc. to which the chain tensioner of FIG. 1 is applied.

  Hereinafter, an embodiment in which the present invention is applied to a hydraulic chain tensioner provided in an automobile internal combustion engine will be described with reference to the drawings.

  Referring to FIG. 5, the cam driving chain 1 is stretched between a crank sprocket 2 attached to the crankshaft and two cam sprockets 3 and 4 attached to the intake camshaft and the exhaust camshaft. The rotational power of the crankshaft is transmitted to the camshaft. The camshaft rotates once every two rotations of the crankshaft, and drives the intake / exhaust valves along with the rotation.

  The chain tensioner 10 of the present embodiment applies a predetermined tension (tension) to the chain 1 by urging the shoe 5 in the direction in which the shoe 5 is pressed against the chain 1 regardless of environmental changes or deterioration over time. The shoe 5 is fixed to the engine body side such as a chain cover, a cylinder head, and a cylinder block by a bolt 6 at one end side, and is pressed against the chain 1 side by a chain tensioner 10 at the other end side. Reference numeral 7 denotes a chain guide.

  1 to 4, a chain tensioner 10 includes a housing 11, a bottomed cylindrical sleeve 12 attached in the housing 11, and a plunger 13 that slides in the sleeve axial direction X in the sleeve 12. And a spring 14 as a biasing means for biasing the plunger 13 in the chain tension direction (upward direction in the figure) X1 along the sleeve axial direction X. The housing 11 is made of a light-weight and low-cost aluminum alloy and is fixed to the engine body 16 (chain cover, cylinder block, cylinder head, etc.) by two bolts 15 (see FIG. 5). The sleeve 12 and the plunger 13 are made of the same metal material or similar thermal expansion coefficient so as to suppress the change in the size of the gap ΔS1 between the inner peripheral surface of the sleeve 12 and the outer peripheral surface of the plunger 13 due to temperature change. Are formed of different metal materials.

  An oil passage 18 (18A, 18B, 18C) is an engine as a hydraulic pressure supply circuit that supplies hydraulic pressure to a hydraulic chamber 17 defined between the inner bottom surface of the sleeve 12 and the back surface of the plunger 13 facing the bottom surface. The main body 16, the housing and the sleeve 12 are formed respectively. These oil passages 18 communicate with the discharge side of an oil pump (not shown), and the lubricant oil discharged from the oil pump is pumped to the hydraulic chamber 17 via the oil passage 18. The oil passage 18 is provided with a check valve (not shown). The plunger 13 is pushed out from the sleeve 12 in the projecting direction / chain tensioning direction X1 by the hydraulic pressure of the hydraulic oil sealed in the hydraulic chamber 17 and the urging force of the spring 14, and is applied to the chain 1 via the shoe 5 by a predetermined amount. Tension is applied.

  In this embodiment, the sleeve 12 includes a sliding portion 21 having a uniform inner diameter through which the plunger 13 slides through a predetermined gap ΔS1, and a first press-in portion 22 and a second press-in portion 22 that are fixed by press-fitting into the housing 11. And a press-fitting portion 23. These press-fit portions 22 and 23 are provided at positions deviating from the sliding portion 21 in the sleeve axial direction X.

  The first press-fit portion 22 has a cylindrical shape with an oil passage 18C formed therethrough, and the sleeve 12 is inserted into the housing 11 in the direction X2 opposite to the chain tension direction X1 with respect to the sleeve axial direction X. It is provided at a position deviated in the insertion direction X <b> 2, and has an outer diameter smaller than that of the sliding portion 21 and set to a thin shape. That is, the first press-fit portion 22 having a small diameter protrudes coaxially and integrally from the center of the end surface in the insertion direction X2 of the sliding portion 21 in the sleeve 12.

  The second press-fit portion 23 is provided at a position deviating from the sliding portion 21 in the chain tension direction X1 with respect to the sleeve axial direction X. The outer diameter and inner diameter are set larger than the sliding portion 21, and It has a cylindrical shape with an open end.

  Thus, the sleeve 12 is set so that the outer diameter increases in the order of the first press-fit portion 22, the slide portion 21, and the second press-fit portion 23 from the insertion direction X1 to the chain tensioning direction X2. Here, on the inner peripheral surface and the outer peripheral surface of the sleeve 12, a tapered portion 24 formed of an inclined surface that gradually increases in diameter from the sliding portion 21 to the second press-fit portion 23 is formed. On the other hand, no such taper portion is formed between the sliding portion 21 and the first press-fit portion 22, and a step surface 25 orthogonal to the sleeve axial direction X is formed.

  In accordance with the shape of the sleeve 12, the first press-fit portion 28 into which the first press-fit portion 22 is press-fitted and the slide portion 21 are slid into the housing 11 to which the sleeve 12 is attached in order from the insertion direction X2. A moving corresponding sliding part 27 having a uniform inner diameter and a second press-fitted part 29 into which the second press-fitting part 23 is press-fitted are formed. A taper corresponding portion 30 that gradually increases in diameter toward the second press-fit portion 29 is formed.

  The sliding corresponding portion 27 is formed in advance with an outer diameter slightly larger than the inner diameter of the sliding portion 21 so that the sliding portion 21 slides smoothly. On the other hand, the first and second press-fit portions 28 and 29 are more than the first and second press-fit portions 22 and 23 so that the corresponding first and second press-fit portions 22 and 23 are fixed by press-fitting. Also, the outer diameter is set slightly smaller. Therefore, by inserting the sleeve 12 into the mounting recess 26 of the housing 11 during assembly, the press-fit portions 22 and 23 are press-fitted and fixed by the respective press-fit portions 28 and 29, and the slide portion 21 is slidable. An appropriate gap ΔS2 is secured between the unit 27 and the unit 27. The gap ΔS1 positioned inside the gap ΔS2 is set to a sufficiently small value.

  The plunger 13 has a bottomed cylindrical shape with a uniform outer diameter that opens at the end on the insertion direction X2 side. The spring 14 is housed inside, and the end of the spring 14 is seated on the chain tensioning direction X1 side. An oil discharge hole 31 is formed through the top. As shown in FIG. 1, the hydraulic oil in the hydraulic chamber 17 is discharged from the inside of the plunger 13 to the outside of the tensioner (inside the engine) through the oil discharge hole 31 as indicated by reference symbols Y1 and Y2, and at the reference symbol Y3. As shown, a part thereof is discharged through the gap ΔS 1 between the sleeve 12 and the plunger 13.

  As described above, according to the present embodiment, the sleeve 12 can be stably press-fitted and fixed to the housing 11 by the press-fit portions 22 and 23 at the upper and lower portions with the slide portion 21 interposed therebetween. Since a predetermined gap ΔS2 is ensured between the sliding corresponding portion 27, the sliding portion 21 is not deformed, in particular, the inner diameter is not reduced during press-fitting. As a result, the inner diameter of the sliding portion 21 of the sleeve 12 can be managed with high accuracy. As a result, the gap ΔS1 between the inner peripheral surface of the sliding portion 21 of the sleeve 12 and the outer peripheral surface of the plunger 13 is set sufficiently small. The hydraulic oil does not leak excessively through the gap ΔS1. As a result, the hydraulic pressure in the hydraulic chamber 17 can be maintained appropriately, and due to insufficient load on the plunger 13 due to excessive oil leakage from the gap ΔS1, or due to an insufficient amount of oil in the hydraulic chamber 17 when starting the engine. The generation of abnormal noise due to the collision between the back surface of the plunger 13 and the bottom surface of the sleeve 12 does not occur.

  Further, since a sufficient gap ΔS2 is ensured between the sliding portion 21 of the sleeve 12 and the sliding corresponding portion 27 of the housing 11, the housing 11 is made of a different material from the sleeve 12, more specifically, light weight. Even if it is made of an inexpensive aluminum alloy, the difference in thermal expansion can be absorbed by the gap ΔS2, and the inner diameter of the sliding portion 21 of the sleeve 12 can be suppressed.

  Furthermore, since it can be assembled by a simple method of press-fitting and fixing, man-hours and costs can be reduced as compared with fixing by casting or fixing using a plug or the like.

  By making the first press-fit portion 22 on the insertion side thinner than the sliding portion 21, dimension management is facilitated, and the press load during press-fit is reduced, and the press-fit operation is facilitated. When inserting the sleeve into the housing, it is only necessary to push the sleeve to a position where the tip surface or step surface 25 of the first press-fit portion 22 abuts the corresponding seating surface on the housing 11 side, and the operation is easy.

  Since the second press-fit portion 23 is provided on the opposite side of the first press-fit portion 22 with the sliding portion 21 interposed therebetween, that is, the sleeve 12 is press-fitted and fixed at two positions above and below the slide portion 21. As shown in FIG. 1, the sleeve 12 does not fluctuate even with respect to the input M in the falling direction from the plunger 13 side that receives input from the chain 1 / shoe 5 side, and is a partial press-fitting structure at two locations. However, the sleeve 12 can be stably fixed to the housing 11.

  Furthermore, since the tapered portion 24 that gradually increases in diameter from the sliding portion 21 to the second press-fit portion 23 is provided, the press-fit operation can be smoothly performed from the slide portion 21 to the second press-fit portion 23 during assembly. .

  As described above, the present invention has been described based on the specific embodiments. However, the present invention is not limited to the above-described embodiments, and includes various modifications and changes without departing from the spirit of the present invention. . For example, in the present embodiment, the press-fitting portions 22 and 23 are provided at two upper and lower portions of the sliding portion 21, but only one of the press-fitting portions may be provided. Or you may make it provide the press-fit part where an internal diameter and an outer diameter are partially large in the middle of a sliding part.

DESCRIPTION OF SYMBOLS 1 ... Chain 10 ... Chain tensioner 11 ... Housing 12 ... Sleeve 13 ... Plunger 17 ... Hydraulic chamber 18 ... Oil path (hydraulic supply means)
21 ... Sliding part 22 ... 1st press fit part 23 ... 2nd press fit part 24 ... Tapered part

Claims (4)

A housing;
A bottomed cylindrical sleeve mounted in the housing;
A plunger that slides in the sleeve axial direction within the sleeve;
A hydraulic pressure supply circuit for supplying hydraulic pressure to the hydraulic chamber between the inner bottom surface of the sleeve and the back surface of the plunger facing the bottom surface, and the plunger is attached to the plunger in the chain tension direction by the hydraulic pressure in the hydraulic chamber. In chain tensioners where power is given,
The sleeve includes a sliding portion having a uniform inner diameter through which the plunger slides through a predetermined gap, and a press-fit portion fixed by press-fitting the press-fit portion of the housing.
The press-fitting portion is provided at a position that is dislocated in a direction opposite to the chain tension direction with respect to the sleeve axial direction from the sliding portion, and has an outer diameter set smaller than the sliding portion. Chain tensioner.   The sleeve is provided at a position deviating from the sliding portion in the axial direction of the chain in the sleeve axial direction, and press-fitted in the sleeve axial direction into a second press-fit portion provided in the housing. The chain tensioner according to claim 1, further comprising a second press-fit portion to be fixed.   The chain tensioner according to claim 2, wherein the second press-fitting portion is set to have an outer diameter larger than that of the sliding portion.   4. The chain tensioner according to claim 3, wherein a taper portion that gradually increases in diameter from the sliding portion toward the second press-fit portion is formed on an inner peripheral surface and an outer peripheral surface of the sleeve.

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